1. Field of the Invention
The invention relates generally to electrical switches and, more particularly, to high voltage, high current disconnect switches for use in isolated phase bus duct.
2. Description of the Prior Art
Disconnect switches in isolated phase bus ducts are used to electrically isolate components such as generators, circuit breakers, and step-up transformers. These switches employ a conductive outer housing at ground potential and an inner conductor disposed within the housing. The housing and inner conductor are adapted to be joined to corresponding housings and center conductors of isolated bus duct. The switches generally employ a fixed and a movable contact to open a circuit through the center conductor in response to actuation by an operating mechanism.
A typical switch is described in U.S. Pat. No. 4,188,515 issued Feb. 12, 1980 to Jayant M. Patel et al. and assigned to the assignee of the present application. The movable conductor consists of a telescoping sleeve assembly axially movable with respect to the center conductor and operated by an acme screw-worm gear-jack located centrally within the switch and driven through a shaft arranged perpendicularly to the longitudinal axis of the switch which penetrates the switch housing and inner conductor. This arrangement requires the shaft to be supported by bearings and electrically insulated from the high potential of the inner conductor. In addition, although the switch generally provides satisfactory performance, it would be desirable to provide a switch having simplified access to the operating mechanism to facilitate maintenance procedures. It would also be desirable to provide a switch which eliminates the problem of maintaining electrical isolation of the inner conductor from ground caused by the penetration of the drive shaft through the housing into the operating mechanism located therewithin.